@JustinVH I just was puzzling with the rotation and found it. The insert point and the snap is working fine know.
The only thing I don't find is how you can connect the arc to the top or down on an other truss.
Like if you connect a c003 corner of prolate to a truss, you can choose the orientation of the corner leg. left, right, down and up. Is this also possible with a single circle arc?

I'm making a circle library for the prolyte H40V series.
I'm trying to get the insertion point @ the right spot of the circle segment.
But I can't figure it out. It stays at the center beginning of the truss segment and the auto connect truss is not working properly .
I real can use some help. Or is there a library with the prolate cirkels and the different segnment of them?